A torque converter may be employed to transfer torque from a drive motor to a transmission in a motor vehicle. The torque converter includes a turbine having an impeller and a turbine wheel, which are at least partially washed by a liquid, so that the rotating impeller drives the turbine wheel. To minimize losses, a converter clutch is also provided, in order to couple the movement of the turbine wheel to that of the impeller mechanically when needed. The transfer of torque takes place, for example, during the driving-off process of the motor vehicle through the hydrodynamic coupling by means of the turbine, and during normal driving operation through the mechanical coupling by means of the converter clutch.
To reduce torsional vibrations around an input shaft of the torque converter during driving operation as much as possible before they reach an output shaft of the torque converter, various systems on and in the torque converter are known, which usually include a centrifugal force pendulum and a torsion damper.
German Patent Application No. 10 2008 057 648 A1 proposes to connect a rotational element having a centrifugal force pendulum to the input shaft by means of a first torsion damper, and to the output shaft by means of a second torsion damper. With this system, it should be possible to better reduce non-uniformities of rotation in the transfer of force between the input shaft and the output shaft.
German Patent Application No. 10 2009 024 743 A1 proposes to attach the centrifugal force pendulum to the turbine wheel, and to provide a torque converter lockup clutch to bridge the turbine when operating under load. A first torsion damper introduces torque into the output shaft from the turbine wheel, and a second torsion damper introduces torque into the output shaft from the torque converter lockup clutch, in this case, the second torsion damper consists of two torsion damper elements, which are arranged in series. The arrangement of the damper elements is intended to contribute to minimizing the construction space needed by the described torque converter.
Torque converters of the described type represent in principle a torsional vibration system which can be set in torsional vibration, for example, by rotational non-uniformities of a motor which drives the drive shaft. The centrifugal force pendulum acts as a rotational speed adaptive absorber, and vibrates in contrary phase to the rotational element on which it is placed. The lower the spring rate of the torsional damper that connects the input shaft to the rotating body, the better the isolation of the rotating body from the input shaft with regard to the rotational irregularities and the smaller the angle of oscillation of the centrifugal force pendulum.
For reasons of design, for example, because of limited available construction space, there is usually only a limited oscillation angle available for the centrifugal force pendulum. Under the influence of strong torsional vibrations, the centrifugal force pendulum may run into a mechanical stop, which can result in very poor isolation of the output shaft from the torsional vibrations. In addition, noises connected with the impacts can be perceived as unpleasant, and the impacts can result in increased wear or fatiguing of the elements in question.
Therefore, it is the object of the invention to specify a hydrodynamic torque converter that has improved resistance to torsional vibrations.